Metal-Surface RFID Tag With Dielectric Intermediary
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Solution Overview
Problem
Existing RFID tags face challenges in maintaining stable performance when attached to metallic surfaces, particularly due to issues with antenna matching and fragile connections, leading to communication disruptions and high production costs.
Innovation Solution
A wireless RFID tag design featuring a loop antenna with direct connection to a semiconductor chip without a matching circuit, using a core resin and antenna sheet wound around it, with specific dimensions and overlap portions to ensure resonance and stability, allowing communication in the UHF band even on metallic surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a dipole-type RFID tag is attached to a metallic surface, then the tag structure is simple, but the antenna stops transmitting radio waves, gain drops, and matching collapses making communication impossible
Solution Approach 1:
A dielectric member is introduced as an intermediary between the dipole antenna and the metallic surface. This dielectric member has a specific dielectric constant and thickness designed to maintain proper impedance matching and antenna radiation characteristics when the tag is attached to metal, thereby enabling communication capability on metallic surfaces while keeping the overall structure relatively simple
2Reliability
If a loop antenna is used to attach to metal surfaces, then communication is maintained on metallic planes, but the antenna requires specific orientation perpendicular to the metal surface and has larger loop dimensions
Solution Approach 1:
Instead of using a loop antenna that must be oriented perpendicular to the metal surface (inverting the conventional approach), the patent employs a dipole antenna with parallel orientation to the metal surface. By introducing the dielectric member with specific electromagnetic properties, the patent inverts the conventional understanding that dipole antennas cannot communicate on metal surfaces, thereby achieving both simple structure and metal surface compatibility
3Ease of manufacture
If an antenna sheet is wound around a dielectric substrate with connected ends, then the RFID tag can be produced, but production cost increases and connection points become fragile and prone to peeling
Solution Approach 1:
The antenna structure is segmented into two separate conductive elements (dipole arms) rather than a continuous wound loop. This segmentation eliminates the fragile connection points where the antenna sheet would need to be joined to itself, while still allowing the antenna to be manufactured using similar winding or lamination processes on the dielectric substrate
4Ease of manufacture
If the antenna sheet ends are connected to the chip terminal, then the RFID tag functions, but the connection point is fragile and could peel off under powerful forces
Solution Approach 1:
The antenna structure is extracted from a continuous wound configuration and separated into distinct segments that can be independently secured to the substrate and chip. This extraction allows for separate optimization of the antenna structure and connection points, enabling more robust connection methods such as separate bonding pads or mechanical anchors that are not constrained by the continuous loop geometry
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The RFID tag achieves stable performance and extended communication distance while being compact and cost-effective, capable of maintaining communication when attached to metal surfaces, with adjustable design to support multiple frequency standards.
Implementation Method 1
A loop plane is installed so as to be perpendicular to a metallic plane. Therefore, mirror current flows on the opposite side of the metallic plane, meaning that the loop antenna has a larger loop than what the loop antenna actually has.
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A wireless tag (1a) includes: a wireless communication circuit (4) that includes first and second terminals coupled to a loop antenna (21) and performs wireless communication using the loop antenna; a first conductor that forms a first curved surface and includes a third terminal disposed at a first end of the first curved surface and coupled to the first terminal, and includes a first area including a second end of the first curved surface; and a second conductor that forms a second curved surface, includes a fourth terminal disposed at a third end of the second curved surface and coupled to the second terminal, and includes a second area including a fourth end of the second curved surface, the second area being parallel to the first area and overlapping (24a) with the first area, the first and second curved surfaces forming the loop antenna.